With today's standard telephone communications services, no one service provides all of the personal communication capabilities desired by a typical telephone subscriber. In general, certain features which are available when using higher-cost services, such as a cellular service, are not available when using lower cost services, such as the landline public switched telephone network (PSTN).
For example, a standard cellular telephone subscriber unit (cellular phone) provides features such as speed dialing, speaker phone (hands-free), and an alpha-numeric display. However, such features are not commonly available on a standard landline telephone.
The situation has even developed to a point where the add-on features available to the users of a low-cost service may not be available to the users of a higher-cost service. For example, a landline subscriber can purchase services such as incoming caller identification (calling ID), but no provision is typically made to provide such calling ID services over the cellular network.
Furthermore, each service now typically requires its own service-specific subscriber device or terminal. That is to say, a landline call cannot be placed using a standard cellular subscriber unit, and a cellular call cannot be placed using a standard landline subscriber unit. Thus, in order to obtain all available telephone features, a person must not only subscribe to more than one service, but must also buy, install, and maintain multiple subscriber units.
Even if a cellular and landline telephone are both installed, the subscriber still must typically give out two or more telephone numbers if he wishes to be reached at all times, when on the road, at home, and in the office. Otherwise, without having arranged for one or more of the numbers to be call-forwarded in advance, a call made to one phone will not be received if the subscriber is physically distant from the subscriber equipment assigned to the called number.
In addition, the subscriber's personal information, such as speed-dialing information, must be programmed into all the subscriber units he uses for each service, and must be reprogrammed each time the information changes.
There are central-office systems being proposed for use in North America and Europe which will implement so-called personal communications services, making it possible to reach any given individual using a single telephone number, regardless of what type of subscriber is available at a given point in time. However, such systems are not currently planned to be implemented commercially until the mid-1990's at the earliest.
U.S. Pat. No. 4,989,230 issued to Gillig et al. and assigned to Motorola, Inc., discloses a cellular cordless telephone which operates with both a standard cordless base unit as well as a standard cellular base station. This device permits the user to connect to the telephone company central office either through the standard cordless telephone or through the cellular system. However, because this device merely combines the features of both devices, it exhibits the shortcomings of existing cellular and residential landline services.